A prefabricated, modular assembly for the building of a timber house, including a plurality of rectangular, panel elements. Each panel element has two rectangular panels each having two oppositely located first sides, and two oppositely located second sides. Each panel element is provided with two parallel, solid wood, continuous girders, each being positioned between and connected to the panels on a respective first side. The panels and the girders collectively form a box. One of the girders projects beyond the panels and the other girder is set back upon the panels by a distance corresponding to the girder projection to form a tongue and groove joint. The panels project beyond the ends of the girders at the second sides to form a continuously extending, rectangular receiving groove. The assembly also includes an orientating beam having a rectangular cross section insertable into a respective receiving groove for orientating the respective panel elements to one another. Adjacent panel elements are connected to each other using the tongue and groove joint. The inserted orientating beam abuts against each respective panel and forms a continuous free space with an end of each respective girder for the receiving of supply lines.